1) I have zone alarm running on both machines is this neccesary given that the router has an inbuilt firewall ?
Having the router will certainly reduce the need to have a firewall, but by no means eliminate it. You should be relatively safe by inbound malicious traffic, but nothing will stop your computer initiating connections, so therefore it would be wise to keep ZA installed on each machine.
2) I cant seem to connect to the network from the laptop but i could when it was wired does it matter one is wireless and one is wired ?
It shouldn't do. I have a DG834G with 2 wired connections and 4 wireless. Everything works fine. What USB adapter do you have? What OS are you using? Are you sure you are in range?
3) What security settings are neccesary via the router wpa or wpa not sure what either means or what settings are reqd for eitther, i found the booklet a bit over my head :-)
Both are methods of encryption and you set an encryption key on the router which you are then required to setup on the wireless device.
I don't use either as I live in the middle of nowhere and I have MAC Authorisation.
Somebody who knows a bit more than I do will no doubt explain the Pros and Cons of WPA and WEP.